Beam forming microphone arrays are frequently used for high fidelity localization or isolation of acoustic sources. Generally, these arrays contain large microphone counts, typically ranging from a few dozen to hundreds.
The operating principle of these arrays derives from the propagation delay from a noise source to a given microphone in the array. Knowledge of the delay time for each microphone in the array can be exploited to resolve the location of an acoustic source. The classical beam forming method involves discrete time-shifting of each digitally acquired microphone signal for localization of acoustic sources, while more modern methods use deconvolution and frequency-domain based signal processing.
Accurate and noise-free localization of sound sources typically requires precise frequency response from the individual microphones in such arrays. In an effort to provide the required accuracy, conventional instrument grade condenser microphones are individually calibrated by the respective manufacturers and exhibit a high degree of precision. However, the cost associated with such individual calibration is considerable.
Less expensive microphone technologies, such as electret or microelectromechanical systems (MEMS), are also available. Such lower cost technologies, however, are typically incapable of providing the necessary sensitivity and matched frequency response among all the microphones in a particular array. Furthermore, the frequency response of most microphones tends to drill when exposed to environmental effects such as temperature and humidity.